Of west orange



March 27, 1928.

N. H. HOLLAND ELECTROMAGNETIC DEVICE Filed Aug. 14. L924 Patented Mar. 27, 1928.

UNITED STATES PATENT OFFlCE.

NEWMAN 'H. HOLLAND, OF WEST ORANGE, NEW JERSEY, ASSIGNOR 'IO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

Application filed August 14, 1924.

. This invention relates to.electromagnetic devices of the balanced armature type such as are used in sound recording and reproducing apparatus.

,The object of the invention is to provide ed iby speech or lllllSlCw-n 1 111; general the invention 'provides slightly bow-(adapting members =oppps'ingzithej mag-v netie pull on-the armature by. longitudinal stresses. dntroduced in; the, springir tension membersi which stressesivary in substantially the same manner as the magnetic; pull, thereby providing a vibratory systemin which the displacement, of the armature is substantially; pro ortionalt0 the amplitude lor the forcegoftie'impressedivibrationsg .Inthe ,preferred embodiment of the. inventi0n,-.t-he. ma 'netic pull on the armature is opposed by forces applied to thervibratory system .through .two slightly bowed tension members disposed on opposite sidesof the axisofoscillation. .When the-armature is in its, normal ,-position, the tension is -.the same in each ioithe m'einb'ers; When the armature isdisplacedimoneflirection from its-normal position the *tensioinin' onegof the ,bowed members; will increase rapidly due to -the tendency-of the ;member to straighten out. When the arinature is displaced in the opposite direction ifrom itsgnor mal position the tension in the other-member willinorease rapidlygfor the ;same reason. Since the forces are applied substantially .longitudinally of the tension members, the longitudinal displacement of-the. ends of-the members attached to ,thewibratgiry-systemis exceedingly small icompared; with the :transverse displacementatthe knee .or .bend in the ten' sioi niembersr .The deflectiondoesnot follow Hooks law; i. e.-,-the;displacement is not 46 directly proportional to the-pull, asin-the case ofsimple springs where the elasticity is constant, but is a function ofelasticity and pull, .both of whichare variable. The tension members may be..-likened to a togglejoint in-which=the-actionds reversed, orto a horizontal line WhlCllrhfiS been deflected by a weight suspended intermediate-the ends thereof. The zlongitudinal stresses .in the line increase rapidly astension is applied to I "ELECTROMAGNETIC DEVICE.

Serial No. 731,952.

lift the weight, and the line approaches the horizontal. According to another feature of the invention, a vibratory system is supported on knife edges by a flexible rod extending through the support parallel to the knife edges,- and a pin through the vibratory mem-. ber engages the rod, which is deflected by adjusting the pinuntil its point of engagement therewith is substantially in line with the axis of oscillation. In the drawings; Figs. 1. 2 and?) are-respectively sectional side and top views'ofa phonograph reprodueer employing the invention: Figs. t'and 5 are enlarged detail views of the invention; Fig. 6 is a fragmentary view showing the support for thevibratory member; Fig. 7-shows the invention applied to driving the diaphragm of a loud speaker; Figs. 8 and 9 show modifications of the invention; and Fig. 10 i's-an end view of the modification shown in-Fig. 9. Referring to the drawings, there is shown a permanent magnet 13 having pole pieces 11 and 12 between which .are supported the usual actuating .coils 14 and 15 which surround opposite ends of the armature- 16 as in .well knownelectromagnetic structures The-armature 16 is sup ported-on a bar ZO-and extends. transversely thereof. A block 18 secured,to the magnet 13-by means of screws His-provided with U shaped extension arms 22, each of which terminates in a knife edge 17 which engages recesses in the bar 20. The arms .22 are provided with 'holes, parallel to the knife edges and at a short distance therefrom, in which is inserted a light flexible rod 23. The bar 20 is provided with a hole perp'endicular to the axis of oscillation in which is loosely fitted a pin 24 provided with an eye'at one end' through which the-rod 23 passes. Theopposite end of the pin 24 is threaded and provided with av nut-25 by means of which rod 23 is deflected preferablyuntil its pointfof engagement with the 100 pin 24 is substantiallyin line with the knife edges 17. The stiffness and mass of the rod 23 do not therefore influence the vibrations of the'armature-lfi.

' Securedto theopposite sidesof block :18 105 by'any suitablemeans such as bolt 26am springs 27 and 28 which have a slight initial bow. The holes in the springs 27 and 28 through which the bolt 26 passes ma be elongated to p royidefor adjustment. The opposite" ends of the springs are secured under the nut 25 to the bar 20. The springs 27 and 28niay be made of one piece and secu i' ed at the center. to the em- 20. They are refer-nit matte oi fiat spring material and given :1 slight bow or deflectionintermediate their supported ends. The initial deflection and the proportions of the springsidepend upon the distance from the axis of oscillation to their point of attachment to the oscillatory member and also upon the' strength of the mzfgneticfield. 1

Since the tension in the springs 27 and 28 increases'verfy rapidly with the'displacenient of the arihatur'et'felose ooupl ing "may be obtained between -it-ancl1the pole: pieces with 'a resulting-increase iii'etliciencyn 7 A'sshqwn in Fig;52 the 'end of the bar 20 may beprovided witha 'stylus holder 30 for a stylus 31, as in the case of-the'ii s ual honograph reproduerfor r'cordenland'the whole the 'spring '37 which in turn exerts tension in the" springs 27- and '28: It will 'be noted that "owing-'10" the double toggle jointarranger'nnt any slight increasein'the tension in the helical spring 37 willsintrbduce 'very large" tensional' "forces in the sprin gs"27 i- 2 t 1 f i i Y ig'sr9 and 10:shov two'views'of another modification in'xvhich the balancing springs 40 and '41, similar to springs-27 and 28, 'a-re attached to tlie end of' thearmature 42 of a receiver such as shown in Patent No. 1.365, 98 nfJanua-ry 18, 1921, to C.

V I i t Altli'ough the invention has been illustrated with sound recording and sound reprbcfiicing appairat-us; it is ob'vious' that it may r'eadil'y' be adapted "to'ariy magnetic structure employing" al balanced arfm'atu're. whatiscl'aimed is:

1. 'I'il' an electroma etic device, a magnet, a 'vibratbryniember' dhiprising an armature adaptedto vibrate in the-'field'of said 'n'iagi'itf and means' "compr'i'si'ng a "spring ten sjio ne'd' lengitudinatly 'gdaptee try-flex in a' p n prpe'ndieularte th afiis 6f oscillatien0'f said-Masteryi'member 'zind'to exert 1 2-111 an electmma netic,(levice a in" ct i tendi w neti zfieldii ii ibrater 511 her comprising an armature aglaptec to "1- ;ibratejin said" magnetic field, and a spring member longitudinally tensioned and having a slight lateral d'efl'ection therein, said member being adapted to flex-in a plane perpen'dicular' tothe axisof oscillation of said member. to oppose the-magnetic pull on the 3. In an electroimlgnetie 'dei'icq a' ma net.

which is small as compared with its'?length;'

one end of said flexible member being; fixed to said mounting and them-herend attached to 'sa'idostillla'tdry' meniber; che 'ongiwdinel displacement of said end attached to s'a'id'o'seillatpry niemberrbeinjg -less"than theua'te'ral displacement of th'e' fl'e'itible" member'a't its bend-for movement's 'bgf''e'id" armature.

4. In an electromagnetic device, a magnet providing a! ifie'ldi'j "an armature disposed therein, and longitudinally"tensionedinieens for balancing gs'akl arrriature "in-Said field, said' i'neiins com ri ing a""sli" htily howed spring "adapted' to s't'raighten land buckle in accordance" with the "oscillations of: 'said infirm-e; y n

55 In an electromagnetic device, amagnet roviding; a field, ar'i erm'atur dis esed therein,' and a air f slightly bowed; engit u'din'ailftefisibned 'spr'irigs'flisposed" one} on each "side of the' axis oi oseill tibner I said armature;ier'ep 'osin thema 'netie'pu-Iren aid a mat re sad-tr springs being elternately stta rigli -tened and buckled in a 'e'o'rd anee 'wi thfthe e'szgi-llatins yet said" "e mituee. 6. *In' an electromagnetiwd viw, a ma net prbvitlinga fie1d,"an armatur adapted-toescil la-tle th rein; in'ea'ns" for balancin said armature in sfaid'jfield, sa id "means eoinpris mg slighuy'eoweds r'ihgs 'on'feac-h "side ef the axis of dil1a.t ie'ri,1"and' means} associated with' 'said' spriligs' intermediatetheirnds for introducing "longitudinal "stresse s'theieinj 91.1 .1 ,I, s

7. In an electromagnetic devic e, amagnet providing a"-fie1d; afi armature 'dispos'ed to oscillate T therein and me ns Ton-balancing saidarmaturein "said fiel 1',"saidmeans- 0in prising "slightl bewed 'sp'ri i je'ne en @3611 side of the a'l'ris at-qgcilletionyflexible "means fol: tyin said' springs tbgetberiptgermeqiate their 'enilsiarrd an auxiliary s'pningeonneeted to silid tying means f 01" exertingtension in said balancing springs.

sion oill'sqund wave enengyge vibratory-$16111 her, a support therefor, means for holding said vibratory member in pivotal relation with said support, said means comprising a flexible rod and means carried by said vibratory member for flexing the center of said rod substantially to the axis of oscillation.

9. In an electromagnetic device, a magnet providing a steady field, a vibratory system adapted to vibrate in said field, slightly bowed tensional members for balancing said system in said field, a support for said vibratory system, and a transversely flexed member for securing said system in pivoted relation to said support the mid-portion of said flexed member being in line with the axis of oscillation.

10. In an electromagnetic device having a magnet and an armature adapted to vibrate in the field of said magnet, a support, a tension member between said armature and said support for compensating for the magnetic pull on said armature, said tension member eing slightly bowed from a perpendicular to the plane of said armature and its axis, the depth of the bow being slight compared with the length of said tensioned member.

11. In an electromagnetic device having a magnetic and an armature adapted to vibrate in the field of said magnet, a support, a tension member between said support and said armature on each side of the axis thereof, said tension members being slightly bowed from a perpendicular to the plane of the armature and its axis, the tension in one of said members increasing rapidly with the displacement of said armature and substantially in accordance with the law of the magnetic pull.

12. In an electromagnetic device, an oscil latory member, a light resilient member having one end attached to said oscillatory member and extending substantially normal to a radius through its point of contact with said oscillatory member and the axis of oscillation, said resilient member having a slight lateral displacement whereby a slight displacement of the armature causes a longitudinal pull in said member for controlling the vibrations of the armature, the displacement of said oscillatory member from its normal position at the point of attachment of said resilient member thereto being less than the lateral displacement of said resilient member for movements of said armature.

In witness whereof, I hereunto subscribe my name this 11th day of August, A. D., 1924.

NEWMAN- H. HOLLAND. 

